The invention relates to an overload protection switch.
The tripping mechanism or latch of an overload protection switch essentially includes a movable contact member which closes the switching path of the switch by lying against one or a plurality of fixed contacts. To ensure rapid switch-off in the case of an overload, the movable contact member is charged with spring tension in the turn-off direction directly or by way of latch components which are articulated thereto. In its OFF position, the contact member is locked directly or by means of latch components--here the so-called trip slide--connected therewith in an articulated manner by means of a locking lever. The latter can be pivoted into its locking position and is pivotal into its unlocking position by means of a thermal and/or electromagnetic tripping member or by the manual actuation of the switch against a resetting force. The movable contact member is fixed in its ON position in that the trip slide, which is hinged to the movable contact member, is supported on an abutment face of the end of the locking lever which, in its locking position, projects into the defined path of movement of the trip slide. The path of movement of the trip slide may here be initiated by it being guided in a housing groove or the like. Also conceivable is a link chain coupling of the trip slide which transfers a structurally required on/off movement of the movable contact member to the trip slide. The only important thing is that during the on/off movement, the trip slide travels a path which is defined with respect to position and direction.
In principle, the overload tripping members of a tripping mechanism need to generate tripping forces to pivot the locking lever into its unlocking position. During the unlocking process, counterforces must be overcome which are composed, inter alia, of friction forces at the point of locking and of leverage forces resulting from the spring charging the locking lever in the locking direction. To ensure rapid response of the overload protection switch and thus high switching performance, these counterforces and thus the tripping forces to be generated by the overload circuit breakers should be kept as small as possible.
In the known solutions of this problem in the art, it is customary, for example, to step down the contact-making and turn-off forces by way of a toggle lever system. Although this brings satisfactory results with respect to the magnitude of the tripping forces to be generated, toggle lever systems are structurally complicated and involve correspondingly high costs for components and installation of the tripping mechanism.